We have previously shown that endochondral ossification is finely regulated by the Clock system expressed in chondrocytes during postnatal skeletogenesis. Here we show a sophisticated modulation of bone resorption and bone mass by the Clock system through its expression in bone-forming osteoblasts. Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1) and Period1 (Per1) were expressed with oscillatory rhythmicity in the bone in vivo, and circadian rhythm was also observed in cultured osteoblasts of Per1::luciferase transgenic mice...

Night eating syndrome (NES) is characterized by caloric intake ≥ 25% of total daily after dinner and/or by two or more weekly nocturnal awakenings accompanied by food ingestion. Causes of NES are not entirely clear and seem to involve a desynchronization between the circadian rhythms of food ingestion and sleep, resulting in a delayed pattern of food intake. Estimates of the prevalence of NES in the general population are around 1.5%, and although much higher frequencies have been described in obese individuals, a causal relationship between NES and obesity is not clearly established...

The brain is considered a major site for microRNA (miRNA) expression; as evidenced by several studies reporting microarray data of different brain substructures. The hypothalamus is among the brain regions that plays a crucial role in integrating signals from other brain nuclei as well as environmental, hormonal, metabolic and neuronal signals from the periphery in order to deliver an adequate response. The hypothalamus controls vital functions such as reproduction, energy homeostasis, water balance, circadian rhythm and stress...

Circadian clocks are endogenous timekeeping networks that allow organisms to align their physiology with their changing environment and to perform biological processes at the most relevant times of the day and year. Initial feedback-loop models of the oscillator have been enriched by emerging evidence highlighting the increasing variety of factors and mechanisms that contribute to the generation of rhythms. In this Review, we consider the two major input pathways that connect the circadian clock of the model plant Arabidopsis thaliana to its environment and discuss recent advances in understanding of how transcriptional, post-translational and post-transcriptional mechanisms contribute to clock function...

Endogenous biological rhythms with approximately 24-h periodicity are generated by the circadian clock, in which clock genes coordinate with one another and form a transcriptional-translational negative feedback loop. The precision of the circadian clock is further regulated by multiple post-translational modifications (PTMs), including phosphorylation, ubiquitination, acetylation and SUMOylation. Here, we review current understanding of the regulatory mechanisms of the core clock proteins by PTMs in the mammalian circadian clock...

Metabolic cycles result from the partitioning of oxidative and reductive metabolism into rhythmic phases of gene expression and oscillating post-translational protein modifications. Relatively little is known about how these switches in gene expression are controlled, although recent studies have suggested that transcription itself may play a central role. This review explores the molecular basis of the metabolic and gene-expression oscillations in the yeast Saccharomyces cerevisiae, as well as how they relate to other biological time-keeping mechanisms, such as circadian rhythms...

OBJECTIVE: Depression is often associated with disruptions in sleep and circadian rhythms. We aimed to confirm these relationships via actigraphic assessment in a large, population-based sample, and test whether sex moderates these relationships. METHODS: 418 participants (age 35-85, mean 57.04, SD = 11.47) completed questionnaires and one week of actigraphy, used to calculate sleep and rest-activity statistics including mesor (mean activity level), amplitude (height of rhythm), and acrophase (time of day that rhythm peaks)...

Mammals have evolved an internal timing system, the circadian clock, which synchronizes physiology and behavior to the daily light and dark cycles of the Earth. The master clock, located in the suprachiasmatic nucleus (SCN) of the brain, takes fluctuating light input from the retina and synchronizes other tissues to the same internal rhythm. The molecular clocks that drive these circadian rhythms are ticking in nearly all cells in the body. Efforts in systems chronobiology are now being directed at understanding, on a comprehensive scale, how the circadian clock controls different layers of gene regulation to provide robust timing cues at the cellular and tissue level...

Precise timing of gene transcription is a fundamental component of many biological rhythms. DNA methylation and histone acetylation are two epigenetic modifications that can affect the probability of gene transcription and RNA expression. Enzymes involved in DNA methylation (dnmts) have been shown to exhibit photoperiodic rhythms in expression in the hypothalamus, which coincide with hypothalamic expression of deiodinase type III (dio3), a gene involved in the photoperiodic regulation of reproduction. It is currently unknown whether enzymes involved in histone deacetylation (hdacs) also vary in response to photoperiod, nor have seasonal changes in the circadian waveforms of methylation and/or acetylation enzymes been examined...

PURPOSE: Exercise enhances memory function by increasing neurogenesis in the hippocampus, and circadian rhythms modulate synaptic plasticity in the hippocampus. The circadian rhythm-dependent effects of treadmill exercise on memory function in relation with neurogenesis were investigated using mice. METHODS: The step-down avoidance test was used to evaluate short-term memory, the 8-arm maze test was used to test spatial learning ability, and 5-bromo-2'-deoxyuridine immunofluorescence was used to assess neurogenesis...

The Leydig cell physiology displays a circadian rhythm driven by a complex interaction of the reproductive axis hormones and circadian system. The final output of this regulatory process is circadian pattern of steroidogenic genes expression and testosterone production. Aging gradually decreases robustness of rhythmic testosterone secretion without change in pattern of LH secretion. Here, we analyzed effect of aging on circadian variation of cAMP and cGMP signaling in Leydig cells. Results showed opposite effect of aging on cAMP and cGMP daily variation...

BMAL1 (brain and muscle ARNT-like protein 1, also known as MOP3 or ARNT3) belongs to the family of the basic helix-loop-helix (bHLH)-PAS domain-containing transcription factors, and is a key component of the molecular oscillator that generates circadian rhythms. Here, we report that BMAL1-deficient cells are significantly more susceptible to infection by two major respiratory viruses of the Paramyxoviridae family, namely RSV and PIV3. Embryonic fibroblasts from Bmal1(-/-) mice produced nearly 10-fold more progeny virus than their wild type controls...

With the rapid development of traffic facilities in China, traffic noise pollution is increasingly prominent. This research aims to explore the influences of combined traffic noise on receptors' anxiety. Institute of cancer research mice were exposed to combined traffic noise (CTN) from highway and high-speed railway for 52days, whose day-night equivalent continuous A-weighted sound pressure level (Ldn) was 70dB(A). The impacts of CTN on anxiety were explored by behavior tests and monoamine neurotransmitter assays...

OBJECTIVE: Residence at Zhongshan Station (69°22'24″S, 76°22'40″E) for over 1 year exposes winter-over members to marked changes of light-dark cycle, ranging from the constant daylight of polar days to the constant darkness of polar nights, in addition to geographic and social isolation. This extreme photoperiodic environment may increase the risk of sleep disturbances and circadian desynchrony. The aim of this study was to investigate the circadian rhythm and sleep phase of Chinese winter-over expeditioners at Zhongshan Station...

The role of thyroid hormones (TH) in the central regulation of energy balance is increasingly appreciated. Mice lacking the type 3 deiodinase (DIO3), which inactivates TH, have decreased circulating TH levels relative to control mice due to defects in the hypothalamic-pituitary-thyroid axis. However, we have shown that the TH status of the adult Dio3(-/-) brain is opposite that of the serum, exhibiting enhanced levels of TH action. Since the brain, specially the hypothalamus, harbors important circuitries that regulate metabolism, we aimed to examine the energy balance phenotype of Dio3(-/-) mice and determine whether it is associated with hypothalamic abnormalities...

In recent years, strong evidence has emerged suggesting that insufficient duration, quality, and/or timing of sleep are associated with cardiovascular disease (CVD), and various mechanisms for this association have been proposed. Such associations may be related to endophenotypic features of the sleep homeostat and the circadian oscillator, or may be state-like effects of the environment. Here, we review recent literature on sleep, circadian rhythms and CVD with a specific emphasis on differences between racial/ethnic groups...